Download Patricia Apkarian, Robert Tijssen, Henk Spekreijse, David Reganf

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A MONOCULARE DIPLOPIE
Per categorie chronologisch
1 Algemene literatuur, diagnostiek enz.
W. B. Inglis Pollock
On Monocular Diplopia
The British Medical Journal, Vol. 2, No. 2489 (Sep. 12, 1908), pp. 734-737
ABSTRACT: -
G.J. Schoute
Monokulare Diplopie
Graefes Archive for Clinical and Experimental Ophthalmology, vol. 121, no. 2, 1928, pp.
284-293
ABSTRACT: -
E. F. Fincham
Monocular Diplopia
Br. J. Ophthalmology, Vol 47, 1963, pp 705-712
ABSTRACT: Suitable tests have shown that slight monocular diplopia occurs in a large proportion of eyes
which have normal visual acuity. It has been found in over 40 per cent. of seventy eyes of subjects between the
ages of 18 and 45. Generally one image is fainter than the other and is almost always displaced approximately
vertically upward. The usual amount of displacement is between 3 and 6 min. of arc. Smaller amounts are
probably undetected. Subjective tests and objective measurement show that in such cases the optical system of
the eye has a prism of power about 0vl A in the upper part of the pupil. The prism base is down and the baseapex direction approximately vertical. This prism apparently covers only a small part of the pupil and so causes a
faint secondary image. As irregularity cannot be detected in the corneal or lens surfaces, it is thought that the
effect is due to a refractive index difference in the lens substance. One effect of this irregularity is to cause
asymmetry in the resolving power of the eye, e.g. a Landolt ring is more easily recognized when the gap is
upward, i.e. in the direction of the ghost image.
Raymond E. Records
Monocular Diplopia
Survey Of Ophthalmology, Vol. 24. No 5. March-April 1980, pp 303-306
ABSTRACT: Monocular diplopia may be of external, optical, neurological, neuromuscular, or psychogenic
origin. It may develop spontaneously or it may be induced by surgery or trauma. Because treatment is usually
directed toward the cause, determination of the etiology is important. Useful diagnostic techniques are described,
as are treatment modalities for monocular diplopia of various origins.
Alison Finlay
The differential diagnosis of diplopia
Optometry Today, October 6, 2000, pp 31-40
ABSTRACT: In summary, many patients complaining of diplopia will have conditions that can be appropriately
managed in practice. For example, congenital SO palsies in their first pair of bifocals or varifocals may become
symptomatic, a situation that can be relieved by using separate readers. Other cases will need routine referral, for
example long-standing deviations which are cosmetically unacceptable may be assisted by surgery. Those for
whom the condition is more sinister and require neuro-ophthalmologic investigation are, fortunately, uncommon.
-2The consequences of inappropriate action, however, can be life threatening. When a patient presents complaining
of diplopia, consider the following:
1. Is it monocular or binocular?
2. Is it refractive or due to misalignment of the visual axes?
3. Is it an imbalance of the accommodative/convergence mechanism or the ocular motor system?
4. Is it long-standing or of recent onset?
5. Was the onset gradual or acute?
6. Is there any associated cause, pain systemic symptoms or pathology?
In an adult or a child, recent, acute onse diplopia due to a concomitant or incomitant deviation with an uncertain
aetiology should be referred urgently for a neuro-ophthalmologic investigation.
Victoria S. Pelak
Evaluation of Diplopia: An Anatomic and Systematic Approach
Hospital Physician, March 2004, pp 16-25
ABSTRACT: Evaluation of diplopia can be daunting without a basic understanding of the mechanisms and
anatomy involved in ocular motility. A systematic approach is necessary to uncover the mechanisms of diplopia
and to appropriately direct the work-up and management. With an understanding of the important historical clues
that help one guide and execute the examination, the challenge of evaluating diplopia can be uncomplicated and
rewarding.
2 Diplopie in relatie met optische fouten.
F. H. Verhoeff
My Major Mistakes
Tr. Am. Ophth. Soc., Vol. 62, 1964, pp 100-108
ABSTRACT: -
Patricia Apkarian, Robert Tijssen, Henk Spekreijse, David Regan
Origin of Notches in CSF: Optical or Neural?
Investigative Ophthalmology & Visual Science, Vol 8, No. 3 March 1987, pp 607-612
ABSTRACT: Grating contrast sensitivity was measured across a range of 1 to 32 cycles per degree (c/deg) in
normal observers with a computer-automated method of ascending limits. Monocular contrast sensitivity
functions (CSF) were obtained for vertical, oblique and horizontal orientations, with or without full refractive
correction. Small amounts of astigmatic error resulted in loss of sensitivity at selective spatial frequencies.
Coincident with these CSF "notches" was the presence of monocular diplopia induced, in this study, by the
condition of astigmatic error. Experimental manipulation of the selective spatial frequency losses was possible
by the introduction of slight cylindrical defocus and by changes in grating orientation. Determination of the
angular displacement and orientation of the monocular double images allowed prediction of the spatial
frequencies which would show reduced sensitivity due to partial cancellation of contrast. The close fit between
the predicted and measured sensitivity loss supports the suggestion that refractive error can affect narrowlytuned notches. These results indicate that before the presence of a notch in the CSF can be attributed to neural
abnormality, an optical cause must be eliminated.
Paul Coffeen, David L. Guyton
Monocular Diplopia Accompanying Ordinary Refractive
Errors
American Journal of Ophthalmology, Volume 105, Number 5, May 1988, pp 451-459
ABSTRACT: Monocular diplopia is commonly encountered in ophthalmic practice. We discovered that it could
be induced in nine $2%) of 71 normal eyes with ordinary spherical or astigmatic defocus of the retinal image.
Possible mechanisms responsible for this effect include retinal processing, diffraction effects, and spherical
aberration. By employing geometric blur circle theory and using a simple optical model to photograph the effect,
we concluded that monocular diplopia in the setting of ordinary refractive error is secondary to relatively minor
-3optical irregularity such as spherical aberration. Contour enhancement properties of the retina probably
accentuate this effect'. Ordinary refractive error should therefore riot be overlooked or discounted in patients
with monocular diplopia.
Recensie van dit artikel:
L. Bour, P. Apkarian
Segmented refraction of the crystalline lens as a prerequisite for the occurrence of
monocular polyplopia, increased depth of focus, and contrast sensitivity function notches
J. Opt. Soc. Am. A, Vol. 11, No. 11, November 1994, pp 2769-2776
ABSTRACT: Theoretical computations of modulation transfer functions (MTF's) of the optical system of the
human eye have shown that irregular aberration consisting of a small circular segment with refractive power
slightly different from the surround introduces at higher spatial frequencies (>20 cpd) an enhancement of the
retinal image contrast on flanks of the optimum-focus plane. When the pupil size is larger than 3 mm,
enhancement is substantial; as a result, multiple foci appear at the affected, higher spatial frequencies and
generate a greater depth of focus. The contrast enhancement also produces troughs on either flank of the
optimum-focus plane. With slight coincident defocus (0.5 diopter) of the retinal image of a sine-wave grating,
notches in the MTF curves, with a contrast reduction in the intermediate frequency range of a factor of 2 to 3 and
a low cutoff spatial frequency of -3 cycles/deg, are produced. In our theoretical study, multiple foci, monocular
polyplopia, and increased depth of focus are implicated in the generation of contrast sensitivity function (CSF)
notches. It is demonstrated that CSF notches of optical origin can extend to lower spatial frequencies (<10
cycles/deg). As a result, before the presence of a CSF notch can be attributed to neurological abnormality,
optical factors, including irregular aberrations, must be eliminated.
Lo J. Bour, Patricia Apkarian
Selective Broad-Band Spatial Frequency Loss in Contrast Sensitivity Functions - Comparison
With a Model Based on Optical Transfer Functions
Investigative Ophthalmology & Visual Science, November 1996, Vol. 37, No.12, pp 24752484
ABSTRACT: Purpose. Contrast sensitivity functions (CSFs) were measured under various optical conditions in
healthy observers together with CSFs from selected patients. Threshold increases across the spatial frequency
range were compared with predictions of a theoretical optical model based on modulation transfer functions.
Methods. Contrast thresholds for various spatial frequencies were determined with a computerautomated method
of ascending limits in a control group and a group of patients with various visual pathway diseases ranging from
retinal disorders, such as diabetic retinopathy, to neural disorders, such as multiple sclerosis. For normal control
subjects, simulated contrast sensitivity losses also were effected by manipulating pupil diameter and dioptric
blur. Modulation transfer functions of the eye's optics in polychromatic light were calculated. The wave
aberration function included standard spherical aberration, coma, and small amounts of irregular aberrations.
Results. Experimentally, slight dioptric blur (e.g., 0.4 to 0.75 D) introduced increased CSF thresholds within
either a narrow or broad bandwidth. For the latter, decreased CSF sensitivity occurred across a spatial frequency
range as broad as 1 log unit, from low spatial frequencies (2 cyc/deg), and for pupil sizes equal to or larger than
3 mm. Predictions based on an optical model are qualitatively and quantitatively in agreement with these
findings. Contrast sensitivity losses of the patients were neither specific nor selective to the pathologic condition
at hand. Furthermore, various CSF losses optically induced in the control subjects were indistinguishable from
nonoptically induced pathologic CSF profiles.
Conclusions. Selective broad-band contrast sensitivity loss may be optically induced by slight refractive error.
As a result, selective contrast sensitivity loss at lower and intermediate spatial frequencies concurrent in patients
with various pathologic, neuro-ophthalmologic conditions cannot be a priori attributed to neural factors without
carefully controlled
-4Russell L. Woods, Arthur Bradley, David A. Atchison
Consequences of Monocular Diplopia for the Contrast Sensitivity Function
Vision Res., Vol. 36, No. 22, 1996, pp 3587-3596
ABSTRACT:
Russell L. Woods, Arthur Bradley, David A. Atchison
Aberrations and Hyperopic Defocus
Vision Res., Vol. 36, No. 22, 1996, pp 3597-3606
ABSTRACT:
Karoline Munson, Xin Hong, and Larry N. Thibos
Use of a Shack-Hartmann Aberrometer to Assess the Optical Outcome of Corneal
Transplantation in a Keratoconic Eye
Optometry and Vision Science, Vol. 78, No. 12, December 2001, pp 866-871
ABSTRACT: We report the optical outcome of corneal transplantation treatment on a keratoconic eye as
measured with a Shack-Hartmann aberrometer, and we compare the results with the recovery of visual acuity
after surgery. Before surgery, the naked keratoconic eye exhibited extremely large aberrations that could not be
measured unless the patient wore a rigid gas-permeable contact lens. With the lens, the computed point-spread
function of the eye was large and multimodal, and simulated retinal images confirmed the patient’s subjective
report of multiple, overlapping images. After full recovery from surgery, aberrations of the corrected eye were
much smaller compared with the presurgical eye, which implied a more compact point-spread function and
clearer retinal images. These optical changes were mirrored by an improvement in uncorrected visual acuity
from 1.3 logarithm of the minimum angle of resolution (logMAR) before surgery to 0 logMAR with spectacle
-5correction after full recovery. We conclude that the Shack-Hartmann aberrometer provides an objective,
quantitative assessment of the optical outcome of penetrating keratoplasty that allows the clinician to measure
retinal image quality objectively and to accurately simulate the complex visual distortions associated with
keratoconus.
Alex Melamud, Maria Regina Chalita, Ronald R. Krueger, Michael S. Lee
Comatic aberration as a cause of monocular diplopia
J Cataract Refract Surg, Vol 32, March 2006, pp 529-532
ABSTRACT: Three patients (5 eyes) presented with complaints of monocular diplopia and no history of ocular
trauma or surgery. The patients had comprehensive neuroophthalmic evaluation including manifest refraction,
anterior segment and dilated fundus examination, and corneal topography. All patients also had wavefront
analysis using the LADAR Wave system (Alcon). Two patients (4 eyes) also had hard contact lens
overrefraction. The patients had a normal initial examination including corneal topography. One patient (2 eyes)
did not experience resolution of diplopia with pinhole. No eye improved with manifest refraction or hard contact
lens overrefraction. However, each patient had a significant amount of coma on wavefront analysis. Moreover,
eyes with horizontal diplopia had horizontal coma and eyes with vertical diplopia had vertical coma as measured
with the wavefront device. Higher-order optical aberrations such as coma may be associated with monocular
diplopia. Wavefront technology may be useful in the workup of monocular diplopia.
Takashi Fujikado, Hiroshi Shimojyo, Jun Hosohata, Yoko Hirohara, Toshifumi Mihashi,
Naoyuki Maeda, Yasuo Tano
Wavefront Analysis of Eye With Monocular Diplopia and Cortical Cataract
American Journal of Ophthalmology, Vol. 141, No. 6, June 2006, pp 1138-1140.e1
ABSTRACT: PURPOSE: To determine whether higher-order aberrations can explain the monocular diplopia
reported by a patient.
DESIGN: Observational case report.
METHODS: A patient complaining of monocular diplopia was examined with the Hartmann-Shack aberrometer
to determine if the higher-order wavefront aberrations could account for the diplopia. The patient had a mild
cortical cataract, and measurements were made before and after lensectomy. In addition, the retinal image was
simulated using Zernike polynomials.
RESULTS: Spherical aberration (0.20 μm for 4-mm pupil) and secondary astigmatism (-0.12 μm) were
increased in the eye. The simulated retinal image had a double configuration that was approximately the same as
the subjective image reported by the patient. After cataract surgery, the diplopia disappeared, and the spherical
aberrations and secondary astigmatism were considerably decreased.
CONCLUSIONS: The monocular diplopia probably stemmed from the combined effects of spherical aberration
and secondary astigmatism caused by the cortical cataract.
Steven M. Archer
Monocular Diplopia Due To Spherocylindrical Refractive Errors (An American
Ophthalmological Society Thesis)
Trans Am Ophthalmol Soc 2007;105:252-271
ABSTRACT: Purpose: Ordinary spherocylindrical refractive errors have been recognized as a cause of
monocular diplopia for over a century, yet explanation of this phenomenon using geometrical optics has
remained problematic. This study tests the hypothesis that the diffraction theory treatment of refractive errors
will provide a more satisfactory explanation of monocular diplopia.
Methods: Diffraction theory calculations were carried out for modulation transfer functions, point spread
functions, and line spread functions under conditions of defocus, astigmatism, and mixed spherocylindrical
refractive errors. Defocused photographs of inked and projected black lines were made to demonstrate the
predicted consequences of the theoretical calculations.
Results: For certain amounts of defocus, line spread functions resulting from spherical defocus are predicted to
have a bimodal intensity distribution that could provide the basis for diplopia with line targets. Multimodal
intensity distributions are predicted in point spread functions and provide a basis for diplopia or polyopia of
point targets under conditions of astigmatism. The predicted doubling effect is evident in defocused photographs
of black lines, but the effect is not as robust as the subjective experience of monocular diplopia.
-6Conclusions: Monocular diplopia due to ordinary refractive errors can be predicted from diffraction theory.
Higher-order aberrations—such as spherical aberration—are not necessary but may, under some circumstances,
enhance the features of monocular diplopia. The physical basis for monocular diplopia is relatively subtle, and
enhancement by neural processing is probably needed to account for the robustness of the percept.
Guillermo M. Pérez, Salomé Abenza, Alvaro De Casas, Jose M. Marín, Pablo Artal
Cause of Monocular Diplopia Diagnosed by Combining Double-pass Retinal Image
Assessment and Hartmann-Shack Aberrometry
Journal of Refractive Surgery Vol. 26, No. 4, 2010, pp 301-304
ABSTRACT: PURPOSE: To report an advanced optical procedure developed for the diagnosis of a particular
case of diplopia.
METHODS: This approach combined the quantifi cation of the level of intraocular scattering by using an
Objective Scatter Index provided by a double-pass instrument (Optical Quality Analysis System) with the
analysis of higher order aberrations using a Hartmann-Shack wavefront sensor.
RESULTS: The value of the Objective Scatter Index revealed increased intraocular scattering; the HartmannShack images showed the existence of an optically differentiated area at the upper region of both crystalline
lenses. Simulation of retinal images computed from the wavefront maps confi rmed that, under low luminance
conditions, this inhomogeneous region of the lens was included in the pupil, generating a secondary image and
therefore the diplopia.
CONCLUSIONS: This report demonstrates the potential of combining two objective optical methods to show
the presence of minor lens opacities that may severely degrade quality of vision.
3 Diplopie specifiek in relatie met hoornvlies afwijkingen.
John F. Dashiell
Monocular Polyopia Induced by Fatigue
The American Journal of Psychology, Vol. 72, No. 3 (Sep., 1959), pp. 375-383
ABSTRACT: This paper describes several cases of monocular polyopia induced by fatigue (ocular work) and it
attempts to determine the physiological bases of the phenomenon. This phenomenon seems to have escaped
notice, as no reference to it can be found in the psychological or ophthalmological literature.
K.J. Bowman, G. Smith, L.G. Carney
Corneal Topography and Monocular Diplopia Following Near Work
Am. J. of Optometry & Physiological Optics, Vol. 55, No. 12, December 1978, pp. 818-823
Corine van de Pol. Henry H. Tran, Dan. D. Garcia, Stanley A. Klein
Three-Dimensional Analysis of Corneal Image Forming properties: A Monocular Diplopia
Example
Proc. Abstract for Vision Science and Its Application Meeting, Santa Fe, NM, Feb. 6-9, 1998
ABSTRACT: The method presented displays cross-sectional slices of image planes produced by ray tracing an
entire cornea. The diplopia example shows quantitative agreement with psychophysical measurements
Charles Campbell
Corneal Aberrations, Monocular Diplopia and Ghost Images: Analysis Using Corneal
Topography
-7Optometry and Vision Science, Vol. 75, No. 3, March 1998, pp 197-207
Karl C. Golnik, Eric Eggenberger
Symptomatic Corneal Topographic Change Induced by Reading in Downgaze
Journal of Neuro-Ophthalmology, Vol. 21, no. 3, 2001, pp 199–204
ABSTRACT: Objective: To elucidate the cause of monocular blur or diplopia after reading in downgaze.
Methods: Corneal topography was obtained before and after a 15- to 30-minute reading effort in downgaze in
three symptomatic patients and in nine asymptomatic control subjects.
Results: Changes in corneal topographic color maps, corneal uniformity index, and predicted corneal acuity were
found in the symptomatic patients but not in the control subjects before and after reading.
Conclusion: Changes in corneal topography can occur after prolonged reading in downgaze and may produce
symptoms of blur or monocular diplopia.
Tobias Buehren, Michael J. Collins, Leo Carney
Corneal Aberrations and Reading
Optometry and Vision Science, Vol. 80, No. 2, February 2003, pp 159-166
ABSTRACT: Purpose. To investigate the effects of eyelid pressure on corneal shape and corneal aberrations
during reading.
Methods. Twenty young subjects with normal ocular health were recruited for the study. The experiment was
conducted early in the morning, with subjects instructed not to perform any prolonged reading before the
experiment. Corneal topography of one eye was measured with a videokeratoscope before reading and then
again after a 60-min reading task. The natural position of the eyelids was photographed in primary gaze and
during the reading task.
Results. Twelve of the 20 corneas showed significant changes in central topography immediately after reading.
The location of the changes corresponded closely to the position and angle of the subject’s eyelids during
reading. The change in shape was best described as a wave-like distortion that significantly altered some corneal
wavefront Zernike coefficients. There was a significant correlation between the changes in primary vertical coma
and trefoil (along 30°). Within the central 6 mm of the cornea, there were significant changes in the root mean
square error, overall refractive power, and astigmatism.
Conclusions. The changes we observed in corneal topography appear to be directly related to the force exerted
by the eyelids during reading. Because the cornea is the major light-refracting surface of the eye, the optical
characteristics of some eyes can be significantly changed during reading by the force of the eyelids. These
findings may have important implications for the definition of refractive status and may also aid in the
understanding of the relationship between reading and the development of refractive errors.
4 Een bijzondere vorm: triplopie.
David A. Goss, Roger W. West, Leland W. Carr, Linda L. Edmonson
A Case of Monocular Triplopia of Lenticular Origin
Optometry and Vision Science, Vol. 69, No. 6, 1992, pp 486-488
ABSTRACT:
-8-
Takashi Fujikado, Teruhito Kuroda, Naoyuki Maeda, Aya Kim, Yasuo Tano, Tetsuro
Oshika, Yoko Hirohara, Toshifumi Mihashi
Wavefront Analysis of an Eye With Monocular Triplopia and Nuclear Cataract
American Journal of Ophthalmology, Vol. 137, No. 2, February 2004, pp 361-363
ABSTRACT: PURPOSE: To determine whether higher-order aberrations explain patient-reported monocular
triplopia.
DESIGN: Observational case report.
METHOD: A patient complaining of monocular triplopia was examined with a Hartmann-Shack aberrometer to
determine whether higher-order wavefront aberrations could account for the triplopia. The patient had a mild
nuclear cataract; measurements were made before and after lensectomy. The retinal image was simulated using
the Zernike polynomials.
RESULT: Spherical aberration (-0.18 μm, 4 mm pupil) and trefoil aberration (-0.16 μm) were increased. The
simulated retinal image had a triple configuration similar to the subjective image reported by the patient. After
cataract surgery, the subjective triplopia disappeared; spherical, and trefoil aberrations were markedly decreased.
CONCLUSION: The monocular triplopia probably stemmed from combined effects of spherical and trefoil
aberrations caused by the nuclear cataract.
James R. Keane
Triplopia - Thirteen Patients From a Neurology Inpatient Service
Arch Neurol, Vol 63, March 2006, pp 388-389
ABSTRACT: Background: Seeing triple is a rare complaint, so anatomically unlikely that it is often considered a
diagnostic symptom of hysteria.
Objective: To evaluate the complaint of triple vision among a large group of neurological inpatients.
Design: Personal case series during a 34-year period.
Setting: Neurology and neurosurgery wards of the University of Southern California–Los Angeles County
Medical Center.
Patients: Thirteen patients who reported seeing objects in triplicate.
Results: Eleven of 13 patients had ocular motor findings, including third nerve palsy in 5 patients, internuclear
ophthalmoplegia in 4, and sixth nerve palsy in 2. Causes included brainstem infarction in patients; ischemic
mononeuropathy, trauma, surgery, and hysteria in 2 patients each; and tumor in 1 patient.
Conclusion: Triplopia is a rare complaint that, in a neurology inpatient service, often represents an an unusual
interpretation of abnormal eye movements.
Aya Kim, Kenichiro Bessho, Yoshitaka Okawa, Naoyuki Maeda, Yasuo Tano, Yoko
Hirohara, Toshifumi Mihashi and Takashi Fujikado
Wavefront analysis of eyes with cataracts in patients with monocular triplopia
Ophthal. Physiol. Opt., Vol 26, No. 1, 2006, pp 65-70
ABSTRACT: Purpose: To determine whether wavefront analysis using a Hartmann–Shack (H-S) aberrometer
can reveal the cause of monocular triplopia in eyes with mild cataracts.
Methods: Six patients (nine eyes; age range 38–58 years; average 49.8 ± 6.9 years) who complained of
monocular triplopia at the Osaka University Hospital between January and December 2003 were examined.
Wavefront analyses of ocular and corneal aberrations of the central 4 mm diameter were performed using a H-S
aberrometer equipped with a Placido ring videokeratoscope. The ocular and corneal higher-order wavefronts
were fitted with a fourth-order Zernike expansion.
Results: All nine eyes showed mild nuclear cataract and had a mean spherical refractive error of -10.3 ± 3.5 D.
The visual acuity was ≥ 20/40 except in one eye with glaucoma. For the Zernike polynomials, the trefoil
aberration (C3-3) and the spherical aberration (C40) were significantly higher than those of age-matched normal
-9controls (p < 0.001). The simulated retinal image of a Landolt C showed that the combination of trefoil
aberration and the spherical aberration can cause an image with a triple configuration.
Conclusions: Monocular triplopia was reported by middle-aged patients with mild nuclear cataract and high
myopia. Wavefront analyses suggested that the triple configuration was caused by the combined increase of the
trefoil and spherical aberration in lenses with mild nuclear cataracts.
5 Andere oorzaken van diplopie.
G. E. De Schweinitz
Concerning Monocular Diplopia, With Cases.
Trans Am Ophthalmol Soc., 1894, 7, pp 233–239.
ABSTRACT: -
T. Harrison Butler
A Case of Monocular Diplopia
The British Journal Of Ophthalmology, 1927, pp 563-564
ABSTRACT: -
J.C. Meadows
Observations on a Case of Monocular Diplopia of Cerebral Origin
Journal of the neuroloyical Sciences, Vol. 18, 1973, pp 249-253
ABSTRACT: A patient with monocular diplopia and a field defect attributable to a localized occipital lobe
infarct is described. The diplopia was of a transient, drifting type; fixation on any small object gave rise to two
overlapping images, the less distinct of which drifted over a period of about 2 sec into an area of relative visual
impairment where it disappeared. No evidence of defective fixation was found to support the usually quoted
explanation of this illusion~hat increased movements of fixation cause a false macula to develop, the image from
which conflicts with that of the true macula.
Daniel K. Roberts
Bilateral Monocular Diplopia Secondary to Occult Diabetes Mellitus
Optometry and Vision Science, Vol. 68, No. 9, September 1991, pp 743-746
ABSTRACT: A 86-year old man presented with transient, bilateral, vertical, monocular diplopia as an initial
manifestation of diabetes mellitus. The diplopia was determined to be of lenticular origin, but was not found to
be secondary to the usual refractive changes. Rather, it is presumed to be due to prismatic alterations caused by
index of refraction differences within the crystalline lenses. It is not known what other factors relate to the
development of this type of diplopia in the diabetic patient.
Charles Campbell
Observations on the optical effects of a cataract
J Cataract Refract Surg, Vol 25, July 1999, pp 995-1003
ABSTRACT Purpose: To describe and measure the optical effects seen by a person with a cataract and to use
these observations to deduce physical changes in the crystalline lens caused by the cataract formation.
Setting: Humphrey Systems, Dublin, California, USA.
Methods: Caustic patterns created on the retina by a bright point source of white light as that source is viewed at
various far-point distances ranging from the anterior focal point of the eye to 115.00 diopters were observed. The
subtended retinal angle of a diffractive ring of light created by a small bright source of white light was observed
and measured.
Results: Three optical effects were seen and measured: multiple-image formation at certain far-point positions; a
diffractive light ring surrounding small bright sources; a radial needle of bright light surrounding a small brightwhite source. With a point source of light positioned at the anterior focal point of the eye, the Y sutures of the
- 10 lens could be visualized. With the point source at other distances, characteristic caustic patterns could be
visualized, allowing assessment of the lens’ optical character. The subtended retinal angle of the diffractive ring
was measured so the periodic lens structure could be evaluated.
Conclusions: The lens acted refractively as if it were divided into 3 elements with noncoincident optical axes.
These 3 segments were associated with areas defined by the Y sutures, causing 3 images to be formed at certain
distances. The caustic patterns indicate that each segment is slightly toroidal with axes at about 120 degrees apart
combined with overcorrected spherical aberration. The period structure creating the diffractive ring had a period
of 10 mm, approximately the width of a cortical lens cell, indicating that fluid between the cells likely creates a
diffractive phase
Valeria Nagy, Laszlo Modis, Katalin Kertesz, Peter Vamosi, Erzsebet Balazs, Andras Berta
Anterior polar cataract as a cause of monocular diplopia
J Cataract Refract Surg, Vol 30, July 2004, pp 1596-1597
ABSTRACT: -
José Javier García Medina, Manuel García Medina, María Dolores Pinazo Durán, María
Morales Suarez-Varela
Monocular diplopia after neodymium YAG laser capsulotomy
Graefe’s Arch Clin Exp Ophthalmol, Vol. 243, 2005, pp 1288–1290
ABSTRACT: Purpose: To present an unusual complication of posterior capsulotomy such as monocular diplopia
and to discuss the importance of capsulotomy size.
Methods: Case report: A 57-year old man came to our clinic complaining of horizontal monocular diplopia in his
right eye for the past 3 days. The patient had undergone a Nd:YAG capsulotomy in this eye 3 weeks before. Slitlamp biomicroscopy under pupil dilation revealed a small capsulotomy and a considerable Elschnig pearl as the
presumable cause of the diplopia. The rest of the examination was completely normal.
Results: After repeat Nd:YAG capsulotomy treatment, the diplopia disappeared.
Conclusion: Capsulotomy size is a significant factor to consider when treating a posterior capsular opacification.
A capsulotomy that is larger than the pupil diameter under scotopic conditions may avoid disturbances of vision
such as monocular diplopia.
B AANVERWANTE ZAKEN
Per categorie alfabetisch op auteur
6 Aberratie algemeen
Raymond A. Applegate, Larry N. Thibos, Gene Hilmantel
Optics of aberroscopy and super vision
J Cataract Refract Surg, Vol 27, July 2001, pp 1093-1107
ABSTRACT: This paper (1) reviews the fundamental limits to visual performance imposed by optical imaging
and photoreceptor sampling to determine the limits to the potential gains offered by ideal corrections; (2)
examines the predicted losses in vision induced by chromatic aberration, phase shifts, typical ocular aberrations,
and the gains possible by correcting the monochromatic aberrations of the eye; (3) discusses the principles of
aberration measurement in the eye; and (4) presents methods for measuring and classifying monochromatic
aberrations of the eye.
Janneke Bus
Hogere Orde Aberraties bij Keratoconus
Examenopdracht Hogeschool Utrecht, Afdeling Optometrie, Juni 2006
- 11 CONCLUSION: Wanneer dit allemaal op een rijtje staat, blijkt een duidelijke toename in de hogere orde
aberraties bij een keratoconus. De verschillende onderzoekers hebben deze toename gerelateerd aan de visus of
de visuele prestatie onder verschillende omstandigheden. Geen van de onderzoeken had een grote
onderzoeksgroep, maar de resultaten wijzen consequent in dezelfde richting en geven een significant verschil in
hogere orde aberraties. Met name de onderzoeken van Pesudovs e.a. (2004) en Gobbe e.a. (2005) geven een
goede indicatie met een wat ruimere opzet en een goede controle groep daarnaast. In dat zelfde onderzoek van
Gobbe e.a. (2005) en in een onderzoek van Marsack e.a. (2006) is er ook onderscheid gemaakt tussen de
verschillende ordes. Hieruit blijkt dat de derde en vierde orde aberraties (coma en sferische aberraties) een
significante verhoging laten zien, waardoor daar zelfs een diagnostische waarde aan gegeven kan worden (figuur
16). Bij een toename van de corneakromming (>60 dpt) blijkt dat de aberraties hoger dan de vierde orde steeds
belangrijker worden (Marsack e.a. 2006). Antwoord gevend op de onderzoeksvraag of er een toename is van
hogere orde aberraties bij keratoconus patiënten kan dat alleen maar een ja zijn. Dit lijkt een conclusie die je aan
de hand van logisch redeneren ook kunt stellen, maar de impact hiervan is vooral praktisch gezien belangrijk. Uit
de diverse onderzoeken die in hoofdstuk 3 beschreven staan blijkt een duidelijke relatie tussen de toenemende
hogere orde aberraties en de afnemende visuele prestatie. Dat deze afname duidelijker naar voren komt onder
laagcontrast omstandigheden geeft een goed beeld van de realiteit. De visuskaarten die normaliter gebruikt
worden hebben een hoog contrast waardoor ze niet altijd een bevestiging geven voor de visuele klachten die
door de hogere orde aberraties kunnen ontstaan. De praktische waarde van deze conclusie is de oplossing.
Wanneer een probleem duidelijk naar voren komt en de oorzaak aan te wijzen is, dan kan er aan de oplossing
worden begonnen. Een klein stukje daarvan heb ik naar voren willen dragen in het laatste hoofdstuk over de
customized lenzen. Jammergenoeg is er nog niet veel onderzoek gedaan naar de waarde van deze correctie
mogelijkheid en zijn de resultaten nog niet overduidelijk. De in hoofdstuk 4 genoemde onderzoeken van De
Brabander e.a. (2003) en López-Gil e.a. (2003) geven wel hoop voor de toekomst. Voor ons als optometristen is
het van belang op de hoogte te blijven van de ontwikkelingen op dit gebied om zodoende onze klant/patiënt de
beste oplossing te kunnen bieden. De wavefront technologie is daarbij niet uit te wissen en het is goed om de
achtergrond daarvan te kennen om te begrijpen waar je mee bezig bent.
D Robert Iskander, Michael J Collins, Brett Davis, Leo G Carney
Monochromatic aberrations and characteristics of retinal image quality
Clinical and Experimental Optometry 83.6 November–December 2000, pp 315-322
ABSTRACT: Background: Patients use a wide variety of terms to describe the characteristics of their vision.
These descriptions encompass the effects of their eyes’ monochromatic aberrations.
Methods: To illustrate the effect of monochromatic aberrations on the quality of the retinal image, we
mathematically reconstructed the image falling on the retina. This has been achieved by combining the
properties of various scenes with the optical characteristics of the eye.
Results: The effects of some common monochromatic aberrations are illustrated. We also show examples of the
retinal image characteristics for two eyes, one with a decentred corneal apex and a second with a decentred
refractive surgery ablation.
Conclusions: The image reconstruction technique provides a powerful tool for investigating the quality of the
retinal image. It provides the capacity for clinicians to better understand a patient’s visual performance. The
image reconstruction technique can also broaden our knowledge of the effects of various forms of aberrations on
retinal image quality for complex real-world scenes.
Victor Arni de Paz Sicam
Shape and wave aberration measurements using the VU topographer and Scheimpflug
photography
Thesis Vrije Univ., Amstrdam, 17 jan 2007
LARGE ABSTRACT: Specifying the wave aberration of the eye is an important aspect in finding solutions to
improve human vision. The classical approach is limited to correction of two basic refractive errors: defocus and
astigmatism. These refractive errors, also known as lower order aberrations, can easily be corrected by spectacles
and contact lenses. Nevertheless, higher order aberrations also play a role. Recent developments in corneal
refractive surgery and intraocular lens (IOL) implantation show that spherical aberration and coma aberration are
also important. Some studies have shown that mesopic vision is improved by placing an aspheric IOL that
eliminates the spherical aberration of the eye. It is also known that coma aberration is induced by decentration of
IOL’s and thus reducing the quality of vision. Therefore, it is beneficial in these applications that pre-operation
corneal measurements give the correct aberrations. The technology for determining corneal aberrations needs
- 12 development for at least two reasons. These involve measurements on both the anterior and posterior corneal
surface. In ophthalmic practice, the aberration of the anterior surface is usually measured using Placido ring
topographers. In these instruments, skew ray reflections are neglected in reconstructing the corneal shape. As a
consequence, the non-rotation symmetric shape features of the anterior corneal surface are measured
inaccurately. The instrument developed at the Vrije Universiteit (the VU topographer) was designed using a
colored pattern instead of rings as stimulus for reflection. Thus, a one-to-one correspondence between source
points and the captured reflected image points can be established. In principle, because of this property the skew
ray error is eliminated. However, prior to this study, no experimental proof of this has been demonstrated. Thus,
it is one of the objectives of this study to demonstrate by actual experiments that the VU topographer improves
the accuracy of reconstructing the anterior corneal surface. Another important consideration regarding corneal
aberration is the contribution of the posterior surface. Little is known about this. Consequently, a second
objective of this study was to determine the contribution of the posterior surface to corneal wave aberration.
Both objectives will bring more certainty in determining the total corneal aberration. To address the first
objective, a surface reconstruction algorithm was developed for the VU topographer. This surface reconstruction
algorithm uses Zernike polynomials to model the corneal shape. An advantage of using Zernike polynomials is
that the individual components such as astigmatism, coma aberration and spherical aberration are used in
ophthalmic practice. Also shape parameters such as radius of curvature and asphericity can be derived directly
from the Zernike coefficients. The developed algorithm has sub-micrometer accuracy in determining corneal
height. Thus this algorithm is suitable for use in numerical simulations as well as in processing experimental
data. Results of measurements on various surfaces and sample eyes reveal that the VU topographer is superior in
recovering the shape of the anterior corneal surface particularly the non-rotation symmetric features. It was
demonstrated that because of skew ray ambiguity ring topographers give under-estimated value for the
astigmatic power. The underestimation observed is small for regular toric surfaces (about 4%: 0.25 D for a
surface with 6.25 astigmatic power), but the results of this study suggest that the error increases with the degree
of complexity of the surface. The under-estimation of the astigmatic power was measured to be 13% for an eye
that had undergone radial keratotomy. The under-estimation was also observed for other non-rotation symmetric
surface features. On the other hand, the VU topographer is able to give the correct astigmatism and the correct
non-rotation surface feature of the anterior corneal surface. To address the second objective of the study
measurements using Scheimpflug photography were employed. By combining different meridian measurements,
the 3D surface properties of the posterior surface can be reconstructed. This shape information was used to
determine the contribution of the posterior surface to the total corneal aberration. The results show that on
average the total corneal astigmatism is lower than the anterior surface by 31% due to the contribution of the
posterior surface. Also the posterior corneal surface contributes to the total corneal spherical aberration. This
contribution increases with age. The addition to the corneal spherical aberration is 15% at age 65. In order to
specify the correct corneal astigmatism and corneal spherical aberration the contribution of the posterior surface
must be measured. On the other hand, the contribution of the posterior surface to corneal coma aberration is
negligible. This means that accurate measurement of the coma aberration of the anterior surface will be sufficient
to provide information for the total corneal coma aberration. Apart from achieving the objectives of the study,
there are some insights gained in the process. The measurement technique employed for the VU topographer also
has the advantage that it is a non-invasive technique to measure the anterior corneal surface. This has at least
four implications. First, in the clinical set-up a non-invasive procedure is convenient for patients. Second, being
a non-invasive procedure, the surface measurements would reveal the actual state of the cornea in contrast with
invasive techniques such as those that use fluorescein solvents. Adding solvents to the eye would produce
additional uncertainty in reconstructing the actual surface shape. Third, with modifications in some aspects of the
apparatus, this technique could also be extended beyond ophthalmology to industrial applications such as surface
diagnostics. Surfaces to be measured could be mirrors, lenses and other basic components of optical devices.
Fourth, the technique uses only one camera to recover the 3D shape properties of the cornea. Thus, the process is
straightforward and simple as opposed to procedures that use multi-camera systems. It is anticipated that these
multi-camera systems would require more complex mathematical algorithms to arrive at the same accuracy in
reconstructing the 3D shape features of objects. The results from this thesis are helpful in finding ways to
measure in vivo the gradient refractive index profile of the lens. This information could prove useful in studies
on presbyopia and also investigations involving the chromatic aberration of the eye. Because the human lens is
an internal component of the eye, direct measurements are not possible. An indirect way of approaching this
predicament is to combine information from wave-front aberration measurements for the whole eye and combine
it with corresponding information for the corneal contribution. Applying tomography principles, algorithms can
be developed to calculate the refractive index profile of the lens from in vivo measurements. The needed
information for the corneal contribution will be provided for by the VU topographer and Scheimpflug
photography. This is an interesting research activity for the future.
- 13 Sander Sterk
Het corrigeren van sferische aberratie door middel van zachte contactlenzen
Eindexamenopdracht Hogeschool van Utrecht, Augustus 2005
CONCLUSION: In de inleiding van deze scriptie heb ik een vraagstelling neergezet welke ik aan de hand van
verschillende hoofdstukken heb onderzocht. Deze vraagstelling luidde: “Werkt het echt in de dagelijkse praktijk
om de sferische aberratie van het oog te corrigeren met tegengestelde sferische aberratie in zachte
contactlenzen?” Aan de hand van de onderzoeken die tot nu toe zijn verricht met betrekking op dit onderwerp
moet er tot de conclusie worden gekomen dat er op dit moment nog veel praktische beperkingen zijn om de
sferische aberratie van het oog te corrigeren door middel van zachte contactlenzen. Dit zal hieronder nader
verklaard worden. Door Holden et al is aangetoond dat een contactlens, wanneer op het oog geplaatst, vlakker
wordt dan de werkelijke BCR van het oog. De sclera wordt hier als reden gegeven, doordat die veelal een grotere
radius heeft dan de cornea en een zachte contactlens hier mede op rust. Hoeveel sferische aberratie de
zogenoemde lensflexure induceert is niet bekend. Wel komt in de studie van Cox et al naar voren dat zachte
contactlenzen een andere sferische aberratie vertonen wanneer zij op het oog zijn geplaatst dan in lucht.
Hetzelfde wordt bewezen in meerdere studies behandeld in hoofdstuk 5. Verschillende onderzoekers leggen dan
ook een relatie tussen doorbuigen en de verandering van de sferische aberratie van een zachte contactlens op het
oog. Onder andere de Benito et al. vermelden in hun studie dat de traanfilm ook niet vergeten mag worden.
Welke relatie dit alles tot elkander heeft is nog niet bekend. Hier zal meer onderzoek naar moeten worden
gedaan. Een volgend vraagstuk is de correctiewaarde voor de sferische aberratie. In de studie van Kelly et al
wordt aangekaart dat de verschillende brekende oppervlakken in ons oog allemaal een verschillende hoeveelheid
sferische aberratie veroorzaakt. Barbero et al. tonen aan dat bij hypermetropen meer sferische aberratie wordt
veroorzaakt dan bij myopen. In de studie van Atchison et al. wordt daarbij nog aangetoond dat emmetropen ook
geconfronteerd worden met sferische aberratie. In beide studies wordt wel gewezen op het feit dat de mate van
sferische aberratie die aanwezig is verschilt per individu. De mate van hinder veroorzaakt door sferische
aberratie verschilt ook per individu. Dit is te herleiden uit paragraaf 3.1 dat uit verschillende studies is
verzameld. Zo spelen hierbij de grootte van de pupil en diepte van de voorste oogkamer een rol. De hoeveelheid
sferische aberratie per individu is hierbij ook geen constante factor. Zo verschuift namelijk de sferische aberratie
naar de negatieve kant wanneer men accommodeert en positief naarmate met ouder wordt. Dit komt naar voren
in onder andere de onderzoeken van Burns et al. en Atchison et al. Aan de hand van het bovengenoemde kan
geconcludeerd worden dat iedereen een andere waarde aan sferische aberratie heeft, niet iedereen in dezelfde
mate daarvan hinder ondervindt en dat sferische aberratie varieert in iedere individu. Meer onderzoek zal moeten
uitwijzen tot in welke mate het verstandig is de sferische aberratie van het oog te corrigeren. Met het
bovengenoemde kan mede geconcludeerd worden dat het corrigeren van sferische aberratie in een zachte
contactlens niet door een standaard waarde te compenseren is. Dit zal voor ieder individu een andere waarde
moeten bevatten. Ook decentratie van een contactlens is bepalend voor de slagingskans van het corrigeren van
sferische aberratie van het oog. Zo wordt in het onderzoek van Benito et al. en Cox et al. vermeld dat decentratie
niet meer mag zijn dan ongeveer 0.3 mm. Wanneer dit wel het geval is met een contactlens die sferische
aberratie voor het oog corrigeert dan zullen hierdoor andere aberraties van andere ordes geïnduceerd worden en
er zo voor zorgen dat de gezichtscherpte zal dalen zodat het corrigeren van de sferische aberratie van het oog
geen zin heeft. Een ander feit komt naar voren in de studies van Cox et al. en de Brabander et al. Daarin wordt
aangetoond dat bij myopen beter een standaard zachte contactlens gekozen kan worden dan een zachte asferische
contactlens (in lucht). Een negatieve standaard zachte contactlens wordt in de periferie namelijk steeds
negatiever qua sterkte, iets dat negatieve sferische aberratie induceert. In de studie van Barbero et al. komt naar
voren dat de sferische aberratie van een myoop oog juist positief is. Door een standaard negatieve zachte
contactlens op het oog te plaatsen wordt dus de positieve sferische aberratie van het oog gereduceerd. Iets wat
met een zachte asferische contactlens (in lucht) niet het geval is. Een zachte positieve standaard contactlens
daarentegen wordt in de periferie steeds positiever qua sterkte. Dit induceert positieve sferische aberratie. In het
onderzoek van Barbero et al. kwam duidelijk naar voren dat bij hypermetropen zelfs meer positieve sferische
aberratie aanwezig is dan bij myopen. Met een zachte positieve standaard contactlens wordt er dus alleen nog
maar meer positieve sferische aberratie geïnduceerd. Kortom, bij myopen kunnen in zachte uitvoering beter
standaard contactlenzen aangemeten worden en bij hypermetropen zachte asferische contactlenzen (in lucht).
De nieuwste ontwikkeling op de markt zijn asferische contactlenzen die wel asferisch zijn, maar niet in lucht.
Hierbij wordt rekening gehouden met de sferische aberratie van het gemiddelde oog en de sferische aberratie die
geïnduceerd wordt door de contactlens. Helaas zijn van deze contactlenzen nog geen onderzoeksgegevens
beschikbaar om te verwerken in deze scriptie, maar naar aanleiding van de theoretische benadering van de alinea
hierboven zou dit best een uitkomst kunnen bieden voor myopen.
- 14 7 Leeftijdsaspecten
Shiro Amano, Yuki Amano, Satoru Yamagami, Takashi Miyai, Kazunori Miyata, Tomokazu
Samejima, Tetsuro Oshika
Age-related Changes in Corneal and Ocular Higher-order Wavefront Aberrations
American Journal of Ophthalmology, Vol 137, N0. 6 (June 2004), pp 989-992
ABSTRACT: Purpose: To investigate age-related changes in ocular and corneal higher-order wavefront
aberrations and elucidate relative contributions of the cornea and the lens in the age-related changes.
Design: Observational case series.
Methods: Corneal and ocular higher-order wavefront aberrations in the central 6 mm diameter were measured
with videokeratography and the Hartmann-Shack wavefront aberrometer in 75 normal eyes of 75 patients with
a mean age of 43.5 ± 11.7 years (range, 18–69 years). Higher-order wavefront aberrations were calculated with
Zernike polynomials up to sixth order. From the Zernike coefficients, we calculated root mean square (RMS) of
coma and spherical aberration. To examine age-related changes of the polarity of spherical aberration, the
changes of the Zernike coefficient Z40 was also investigated.
Results: Both corneal (r =.307, P =.007) and ocular (r =.334, P =.0033) coma RMS showed positive correlations
with age. There was a positive correlation between corneal and ocular coma RMS (r = .468, P < .0001). The
RMS of corneal spherical aberration did not change with aging (r = .153, P = .1895), whereas the RMS of ocular
spherical aberration had a positive correlation with aging (r = .308, P = .0068).
Conc;usion: These results suggest that the ocular coma increases with age, mainly because of the increase in the
corneal coma, and the ocular spherical aberration increases with age, mainly because of the increase in the
spherical aberration in the internal optics.
Antonio Guirao, Manuel Redondo, Pablo Artal
Optical aberrations of the human cornea as a function of age
J. Opt. Soc. Am. A, Vol. 17, No. 10 (October 2000), pp 1697-1702
ABSTRACT: We investigated how the optical aberrations associated with the anterior surface of the human
cornea change with age in a normal population. Aberrations were computed for a central part of the cornea (4, 5,
and 6 mm in diameter) from the elevation data provided by a videokeratographic system. Measurements were
obtained in 59 normal healthy, near-emmetropic [spherical equivalent lower than 2 diopters (D)] subjects of
three age ranges: younger (20–30 years old), middle-aged (40–50 years old), and older (60–70 years old). The
average corneal radius decreased with age and the cornea became more spherical. As a consequence, spherical
aberration was significantly larger in the middle-aged and older corneas. Coma and other higher-order
aberrations also were correlated with age. The root mean square of the wave aberration exhibited a linear
positive correlation (P < 0.003) with age for the three ranges of pupil diameter. Despite a large intersubject
variability, the average amount of aberration in the human cornea tends to increase moderately with age.
However, this increase alone is not enough to explain the substantial reduction previously found in retinal image
quality with age. The change in the aberrations of the lens with age and the possible loss of part of the balance
between corneal and lenticular aberrations in youth may be the main factors responsible for the reduction of
retinal image quality through the life span.
8 Diversen
P.T.V.M. de Jong
Wat zíét u nu eigenlijk? Visuele stoornissen en nabootsing ervan voor normaal zienden.
Ned Tijdschr. Geneeskunde, 2003, 20 december, 147(51), pp 2540-2550
ABSTRACT: De meeste artsen weten weinig over hoe personen met visuele beperkingen iets waarnemen. Soms
kan men door eenvoudige hulpmiddelen toe te passen een beeld krijgen van wat een dergelijke belemmering
voor de betrokkene betekent, bijvoorbeeld door brillen van verschillende positieve sterkte en lichtdoorlatendheid
zelf op te zetten, of door casuïstische praktijkervaringen, schilderingen en fotosimulaties te bestuderen. Tot deze
laatste behoren een vrouw die afbeeldde wat zij met een verwijderd oog ‘zag’, een man die zonder ogen vanuit
zijn visuele herinnering schilderde, en een schilderij van een protanope schilder die kleuren koos op grond van
de tekst op de verftubes. Zo kan men zich ook een beeld vormen van fantoombeeld, verminderde
gezichtsscherpte, gezichtsvelduitval, metamorfopsie, dubbelzien, verblinding en visuele agnosie. Ook van
- 15 stoornissen in fusie van beelden, dieptezien, stereoscopisch zien, donkeradaptatie en kleurenzien, evenals van
afname van de visuele functies op hoge leeftijd. Dit artikel bevat figuren in kleur, waarmee de stoornissen
worden nagebootst.
Ying-Khay Nio
Defocus-Specific Contrast Sensitivity
Thesis Univ. Groningen, 1 June 2005
LARGE ABSTRACT: It goes without saying that good eyesight has always been important for mankind. The
deterioration of eyesight, therefore, is a drastic event. The two most frequent causes of poor sight are optical in
nature: refractive abnormalities (near-sightedness, far-sightedness, astigmatism, presbyopia) and cataracts.
Refractive abnormalities can be corrected with a great variety of techniques and tools. The most well-known
corrective device is spectacles. A more recent development is the contact lens. It was developed because
spectacles sometimes have practical, optical, or cosmetic drawbacks. Today, we are living in the era of refractive
surgery. A refractive error can now be corrected with lasers or an operation so that spectacles and contact lenses
are no longer necessary. A cataract, a clouding of the lens, can be treated surgically. This procedure has evolved
from the cataract operation conducted by Bartisch in the 16th century in which an opaque lens was pushed out of
the pupil opening and into the vitreous, via a number of intermediate stages, to the current cataract extraction
method in which the lens contents are removed by means of phacoemulsification. Since Ridley’s implantation of
an artificial intraocular lens in 1949, it has also been possible not only to remove an opaque lens, but also to
replace it. Until quite recently, spherical lenses were used in ophthalmology to treat refractive errors and
cataracts. The surface of a spherical lens comprises part of a sphere. The image quality of these lenses is very
mediocre, because it is limited by so-called spherical aberration. This type of aberration occurs when the focal
distance of rays of light through the edge of the lens is shorter than that of rays through the centre.
The reduction of aberrations, in particular spherical aberrations, is currently a relevant research topic. In fact,
refractive surgical laser techniques are being refined for the purpose and intraocular lenses are being developed
that have fewer spherical aberrations. The goal is to achieve a sharper image with a higher contrast.
None of these developments are without danger. Although it is undoubtedly possible to project a sharper, higher
contrast image on the retina, it is unknown whether the human visual system can process it accordingly. The
neural part of the human visual system, for example, is not geared to process such unnaturally good images:
during the process of human evolution, the neural part adapted optimally to the limited quality of eye optics.
Neural undersampling, leading to a misrepresentation of the image, is a possible consequence. A well-known
example of this phenomenon, alias aliasing, is when forward-turning wheels appear to spin backward on TV: a
surplus of information provided to a system with a limited capacity leads to an incorrect interpretation. In
addition, a better image in the focal plane caused by fewer aberrations implies a poorer image outside the focal
plane. This results in a smaller depth of focus, which is clearly disadvantageous for older people with presbyopia
in whom accommodation has been lost and who can no longer focus at different distances without visual aids.
Young people may suffer from asthenopia under the same conditions: it is unknown whether the accommodation
reflex (the mechanism that allows the eye to focus at different distances) can adapt to the new optical situation.
Consequently, there are two reasons why the evaluation of eye optics after refractive or cataract surgery must not
be limited to just objective measurements of optical characteristics during optimal focussing, i.e., in the focal
plane. First, psychophysical (subjective) easurements that also include the neural part of the nervous system,
such as measurements of visual acuity and contrast sensitivity, are essential. Second, measurements must also be
made under defocus conditions, i.e., outside the focal plane, in order to determine the depth of ocus.
This thesis describes contrast sensitivity measurements that were made in healthy control subjects, in patients
who have undergone a cataract operation, and in patients who have been treated with refractive surgery. The
study is innovative in that the measurements were performed not only under wellfocused (corrected for refractive
errors) conditions, but also with different amounts of defocus. As a result it was possible to discuss depth of
focus and, using a theoretical eye model, calculate the spherical and irregular aberrations that are present in the
human eye. Such an approach made it practicable to show the differences between healthy control subjects and
patients after a cataract extraction. There were also clear differences between the healthy control subjects and the
patients who underwent refractive surgery and between the subgroups undergoing different forms of refractive
surgery. The following paragraphs briefly elucidate the most important results of the study.
Chapter 1, the general introduction, presents a number of important basic concepts and explains how eye
aberrations can be calculated from contrast sensitivity measurements.
Chapter 2 details a study aimed at finding an efficient method to measure contrast sensitivity. Contrast sensitivity
measurements test the ability of the eye to detect relative differences in light intensity, which were represented as
a pattern of consecutive darker and lighter bars in this study. Because so many measurements were necessary for
the research described in this thesis (contrast sensitivity with different spatial frequencies, i.e., different widths of
- 16 the darker and lighter bars, different pupil diameters, and different levels of defocus), finding the most efficient
method of measuring was very important. Three existing methods were compared and the so-called von Békésy
method, with a speed of 0.5 log units/s, was finally chosen.
Chapter 3 describes the measurements of 100 healthy control subjects. The results of these measurements served
as reference for the rest of the study. Contrast sensitivity for higher spatial frequencies decreased with age. This
was not the case for lower spatial frequencies. Depth of focus increased with age, which suggests an increase in
aberrations as one ages.
Chapter 4 combines the results from Chapter 3 with the calculations of a theoretical eye model, the eye model of
Jansonius and Kooijman. Spherical and irregular aberrations are the variables in that eye model. After a value
has been set for each variable, the relative modulation transfer (i.e., contrast sensitivity in defocus divided by
contrast sensitivity at optimal focus) of the model is calculated for various conditions (spatial frequencies, pupil
diameters, and defocus). Spherical aberration causes a so-called myopic shift: the optimal correction for low
spatial frequencies differs from that for high spatial frequencies. Spherical and irregular aberrations together
determine the depth of focus. The best match between our measurements and the calculations of the model were
attained for a spherical aberration of circa 1 dioptre with a 6-mm pupil and an irregular aberration of circa 0.5
dioptre.
Chapter 5 compares a group of 11 pseudophakic individuals (after a cataract operation) with healthy agematched control subjects. The pseudophakic individuals had a greater depth of focus than the healthy controls.
Use of the eye model showed that this greater depth of focus was caused by the greater amount of spherical
aberration in the pseudophakic subjects. Differences in irregular aberration were not found. One notable detail
was that the greater depth of focus did not occur at the expense of visual acuity or contrast sensitivity at optimal
focus. No significant differences were found between the groups for either of these parameters.
Finally, Chapter 6 compares a number of techniques for the treatment of myopia (near-sightedness). Intracorneal
ring segments (Intacs™), soft contact lenses, and spectacles were compared in the treatment of low myopia,
while the iris claw lens (Artisan™), LASIK (laser-assisted in-situ keratomileusis), hard contact lenses, and
spectacles were studied in high-myopic subjects. The low-myopic patients with Intacs™ had a greater depth of
focus than those wearing contact lenses or spectacles. This appears to be the result of the larger
amount of irregular aberrations in the subjects with Intacs™. Differences in visual acuity and contrast sensitivity
at optimal focus were not found. The LASIK patients had lower contrast sensitivity at optimal focus than the
other high-myopic patients. This was related to the greater amount of spherical and irregular aberrations seen in
the LASIK patients. There was no greater depth of focus, however. Not one of the surgical techniques performed
better than spectacles.
In conclusion, the patients in this study were treated using techniques that had not been adjusted to lessen
aberrations. The fact that there were obvious differences between the different – albeit relatively small –
(sub)groups suggests that the methodology used in this study is applicable for the evaluation of future
developments in cataract and refractive surgery aimed at decreasing aberrations. Based, for example, on the
results in Chapter 5, however, the emphasis of these developments should lie in the optimization of the
aberrations, not in their minimization. Depth of focus and thus aberrations remain crucial as long as the problem
of presbyopia has not been satisfactorily solved. In the current situation, the techniques aimed at lessening
aberrations are more useful for those patients with a more than average amount of
aberrations as a result of, for example, a corneal disease.
A. Tokovinin, S. Heathcote
Donut: Measuring Optical Aberrations from a Single Extrafocal Image
Publications of the Astronomical Society of the Pacific, Vol. 118, No. 846 (August
2006), pp. 1165-1175
ABSTRACT. We propose a practical method to calculate Zernike aberrations from analysis of a single
lngexposure defocused stellar image. It consists of fitting the aberration coefficients and the seeing blur directly
to a realistic image binned into detector pixels. This “Donut” method is different from curvature sensing in that it
does not make the usual approximation of linearity. We calculate the sensitivity of this technique to detector and
photon noise and determine optimal parameters for some representative cases. Aliasing of high-order modeled
aberrations is evaluated and shown to be similar to a low-order Shack-Hartmann sensor. The method has been
tested with real data from the SOAR and Blanco 4 m telescopes.